The invention concerns a method and device for producing steel strip by belt casting.
A method of this general type for producing steel strip by belt casting is already known (Steel Research 74 (2003), No. 11/12, pp. 724-731). In particular, this method of production, which is known as the DSC method, is suitable for producing hot rolled strip from light-gage steel.
In the known method, molten metal is fed from a feed vessel onto a revolving casting belt via a pouring spout and a siphon-like outlet area designed as a casting nozzle. Intensive cooling of the casting belt causes the poured molten metal to solidify into a near-net strip with a thickness of 6-20 mm. After complete solidification, the near-net strip is subjected to a hot rolling process.
To realize uniform distribution of the melt on the casting belt, several jets of an inert gas in the form of a rake distributed over the width are directed towards the melt bath against the direction of conveyance in the feed area.
A disadvantage of this belt casting installation is that during the operation caking can develop in the outlet-side area of the casting nozzle, which, causes greater and greater reduction of the outlet cross section. This leads to unequal feeding of the molten steel onto the belt and thus to casting defects.
Studies on the cause of the caking have shown that, for one thing, the lower temperature at the casting nozzle compared to the molten metal first makes the formation of deposits possible, and for another, the ceramic casting nozzle is wetted by oxides that form on the surface of the melt as the melt emerges and continue to adhere there and then form an ideal surface for further growth of the caking deposits.
The caking deposits form especially in the critical triple point of ceramic casting nozzle, revolving casting belt and liquid metal melt and in areas with unfavorable flow conditions.